1. Field of the Invention
The present invention relates to an image removing device for peeling off/removing an image forming substance included in an image from a recording material on which the image has been formed by an image forming apparatus such as a copier, a printer, or a facsimile machine. Furthermore, the present invention relates to an image removing method performed by the image removing device, and an image forming/removing system including the image removing device and the image forming apparatus.
More particularly, the present invention relates to an image removing device, an image removing method, and an image forming/removing system including the image removing device and an image forming apparatus, for heat-transferring an image forming substance from a recording material, on which an image including a thermoplastic image forming substance is heat-fixed, onto a peeling member, to remove the image forming substance from the recording material.
An image removing device, an image removing method, and an image forming/removing system according to an embodiment of the present invention are applicable to the technical field of removing an image formed by the most versatile electrophotographic method. Specifically, such an image is formed by forming an electrostatic latent image on a photoconductor made of a photoconducting material, developing the electrostatic latent image into a toner image with the use of a dry type toner, and transferring the toner image onto a recording material. The present invention is also applicable a technical field of removing an image formed by an electrophotographic method or with an electrophotographic device without the use of a photoconductor, but by a method of using toner including a pigment and a high polymer compound dispersed in an insulative liquid medium. Examples are a wet electrophotographic method, an electrostatic recording method, a toner jet recording method, and an ion flow recording method.
The present invention is not limited to a technical field of removing an image from a recording material on which the image is formed by an electrophotographic method; the present invention is also applicable to a recording material on which an image is formed by a magnetic recording process performed by forming an image with the use of a thermoplastic image forming substance, a heat transfer method, or an inkjet method performed by using thermofusible solid ink.
2. Description of the Related Art
In recent years and continuing, printers, analog copiers, digital copiers, and printing machines have become pervasive, and large quantities of paper have been used. Pulp is the raw material of paper sheets that are generally used as recording materials. The pulp is obtained from wood, which is a recyclable resource. However, in the manufacturing process of paper sheets, a large amount of power is consumed in the procedure of extracting cellulose fiber from wood to turn the wood into pulp, and in a papermaking procedure of drying the paper sheets. Attempts have been made to reduce the amount of carbon dioxide gas that is generated when fossil fuel is used. Specifically, fuel derived from biomass has been used in some procedures for manufacturing paper sheets. An example of fuel derived from biomass is black liquor, which is the residuum remaining after the pulp has been extracted from the wood. However, in actual circumstances, biomass-derived fuel is not used in every procedure, and a large amount of fossil fuel is still being used. Carbon dioxide gas generated from fossil fuel is considered to be the causative agent of global warming. Furthermore, depletion of fossil fuel resources needs to be decelerated. Accordingly, in view of environmental conservation, the amount of paper consumption must be reduced. Furthermore, by saving the amount of biomass-derived fuel used in paper manufacturing processes, the biomass-derived fuel can be used for purposes other than paper manufacturing processes.
In recent years and continuing, fewer forests have been recklessly logged for the purpose of manufacturing paper. However, not all paper sheets can be made only of wood obtained from forests that are sustainably managed. Therefore, it is an important social issue to mitigate consumption of paper in order to conserve forests and prevent the global environment from deteriorating.
Furthermore, paper includes inorganic components that cannot be combusted or decomposed. Therefore, every time paper is disposed, waste material that needs to be disposed by landfill is generated at a constant rate. In recent years and continuing, it has become more and more difficult to find areas for landfill to dispose paper. Thus, reduction of paper consumption is a pressing issue.
To address this problem, there is a conventional method of collecting information recording sheets that have become unnecessary, and digesting the paper into the form of pulp at a paper mill, to manufacture recycled paper. However, the problem with this method is that although it does not require new wood resources, the amount of power required in this method for transporting collected paper, digesting the paper into pulp, and manufacturing recycled paper, is the same as the amount of power used for manufacturing paper from fresh pulp. Furthermore, paper made from recycled pulp has inferior quality in terms of rigidity and whiteness, and smudges appear when characters are printed. Thus, in high-quality paper used as information recording paper, the ratio of recycled pulp needs to be no more than around 30%. In order to manufacture high-quality information recording paper having a high level of whiteness, there is a need to minimize the ratio of pulp extracted from waste paper, and to manufacture the pulp from unused waste paper. As a result, it is generally likely that the cost would exceed the cost for manufacturing paper from new wood, and the environmental load would increase. Moreover, recoding materials on which recorded information is recorded, are collected from companies and homes, which may be problematic in terms of protecting confidential information and privacy.
A method has been proposed to solve the problems accompanying the operation of collecting used paper and producing recycled paper. Specifically, images are removed from used reusable recording materials, to regenerate these recording materials. For example, patent document 1 (Japanese Laid-Open Patent Application No. H4-64472) discloses an image removing device for removing an image formed on a recording material by transferring it onto a peeling member. Specifically, an endless belt having thermofusible resin provided on its surface is used as a peeling member. An image formed on a recording material is treated with a parting agent. The image is removed from the recording material by being peeled off and transferred to the peeling member with heat. In this disclosed device, the peeling member and the recording material are superposed on each other, to which heat and pressure are applied. The endless belt which is the peeling member is rotated, so that the recording material superposed on the peeling member is conveyed to the position where a cooling roller is provided. Thus, the thermofusible resin on the peeling member and the formed image are cooled. Subsequently, the peeling member and the recording material are separated from each other.
In patent document 1, there is no description of effects achieved by such a configuration. However, according to research conducted by inventors of the present invention, by providing a thermofusible resin layer or a thermoplastic resin layer on the surface of the peeling member, images will contact the peeling member with good performance. Therefore, operations of removing images of low gray scale levels and images with unevenness (in terms of height), and removing images from a recording material with a bumpy surface can be performed with better performance compared to the case of using a peeling member without a thermofusible resin layer or a thermoplastic resin layer. Furthermore, the peeling member and the recording material are superposed on each other and heat and pressure are applied, and then the thermofusible layer on the surface of the peeling member belt is cooled before separating the peeling member and the recording material from each other. Accordingly, the cohesive force of the thermofusible resin on the surface of the peeling member is increased. Therefore, when the peeling member and the recording material are separated from each other, cohesion failure is unlikely to occur in the thermofusible layer, so that the thermofusible layer is prevented from being reverse-transferred to the recording material. If the thermofusible layer was colorless or transparent, even when the thermofusible layer is reverse-transferred to the recording material, the recording material from which the image forming substance has been removed can be reused without any inconvenience. However, after repeatedly using the peeling member, the transferred image forming substance will be mixed in the thermofusible layer. Consequently, the thermofusible layer on the surface of the peeling member will have color. If the colored thermofusible resin is reverse-transferred to the recording material, colored resin will adhere to the surface of the recording material from which the image forming substance has been removed.
In the image removing device disclosed in patent document 1, the image removing properties can be enhanced as described above. However, if the recording material had fixing properties that are high enough for having the image forming substance fixed on its surface, it would be difficult to completely remove the image forming substance from the recording material. Furthermore, if an endless belt was used as the peeling member, the belt would become displaced after repeated usage, and the displacement would be difficult to correct. If an attempt was made to forcibly correct the displacement, the peeling member may receive inconsistent tension across its width direction, which would cause the belt to deform, thereby reducing the operating life of the peeling member belt. This reference does not describe any means for removing, from the peeling member, the image forming substance that has been transferred from the recording material to the peeling member. However, it is obvious that the peeling member cannot be repeatedly used without removing the image forming substance that has been transferred from the recording material. Furthermore, if a cleaning unit was provided for removing the image forming substance from the peeling member, there would be at least two nip portions, namely a nip for transferring the image forming substance from the recording material to the peeling member, and a nip between the cleaning unit and the peeling member. With such a configuration, it has been extremely difficult to prevent the peeling member belt from being displaced.
Patent document 2 (Japanese Laid-Open Patent Application No. 2002-72792) and patent document 3 (Japanese Laid-Open Patent Application No. 2001-66957) disclose an image removing device in which the peeling member is a roller and a thermoplastic resin layer is provided on the surface of the peeling member. As described above, by providing a thermoplastic resin layer on the surface of the peeling member, the image removing properties may be improved. However, in such a configuration, the thermoplastic image forming substance that is transferred from the recording material and the thermoplastic resin layer provided on the surface of the peeling member will not maintain their respective layer forms; instead, the thermoplastic image forming substance transferred from the recording material and the thermoplastic resin layer provided on the surface of the peeling member will be combined with each other. Thus, it has been difficult to remove the image forming substance transferred to the peeling member. These patent documents describe a unit for removing the image forming substance on the peeling member by pressing a heated blade against the peeling member. However, even if a unit for heating the blade is provided, the blade will contact a part of the image forming substance that has not been fluidized on the peeling member, at least on the upstream side of the blade. Therefore, a high level of friction will be generated between the blade and the peeling member. As a result, the peeling member may be driven in an unstable (irregular) manner, or the peeling member may be hampered from being driven, or it may be necessary to provide a large motor for generating a large driving force. Moreover, if the width of the contacting part between the blade and the peeling member was reduced in an attempt to solve these problems in driving the peeling member, there would not be enough time to heat and fluidize the image forming substance on the peeling member. Thus, it has been difficult to remove the image forming substance from the peeling member. Furthermore, the processing speed has had to be extremely low in order to secure enough heating time.
In an image removing device using a roller-type peeling member (hereinafter, “roller peeling member”), a heating member such as a halogen lamp is provided inside the roller peeling member. In order to remove the image forming substance on the peeling member with a blade, the image removing device needs to be configured such that the peeling member is not cooled on the upstream side of the portion where the blade and the peeling member contact each other. This is why a heat source is provided inside the roller peeling member, as described in these references. However, if a heat source is provided inside the roller-type peeling member, the following problem may arise. Specifically, the peeling member and the recording material are superposed and heated/pressurized at a nip portion formed between the peeling member and a pressurizing member. It will be difficult to make the position of separating the recording material from the peeling member have a lower temperature than the temperature of the peeling member surface or the image forming substance at this nip portion. Thus, when separating the recording material from the peeling member, a cohesion failure is apt to occur in the image forming substance and the thermoplastic composition layer provided on the surface of the peeling member. Accordingly, it has been difficult to achieve good properties in removing the image and separating the recording material from the peeling member.
Patent document 4 (Japanese Laid-Open Patent Application No. H7-13383) discloses a method of impregnating the paper sheet on which an image has been formed by an electrophotographic method, with a liquid including water, to weaken the adhesive force between the paper sheet and the image forming substance. When the adhesive force has become weak, the paper sheet and the peeling member are heated and pressed against each other, to peel off/remove the thermoflexible image forming substance from the paper sheet. In the method disclosed in this public document, the paper fiber is caused to swell by the liquid including water, so that a shearing force is generated between the paper sheet and the image forming substance that does not swell by the liquid, thereby weakening the adhesive force between the image forming substance and the paper sheet. This is advantageous in that the image forming substance can be transferred to the peeling member even if the adhesive force between the peeling member and the image forming substance is relatively weak. The peeling member described in this public document does not have a thermoplastic composition layer provided on its surface. However, even in an image removing method performed by impregnating the paper sheet with the liquid including water to weaken the adhesive force between the paper sheet and the image forming substance before heat-transferring the image forming substance from the recording material to the peeling member, if there is no thermoplastic composition layer provided on the surface of the peeling member, the image will not sufficiently contact/adhere to the peeling member, which makes it difficult to completely remove the image from the recording material. Particularly, in the case of powder image forming substance particles, low density gradation images, or color images, the image forming substance adheres to the paper sheet in an isolated manner and forms background fogging. Therefore, the image forming substance and the peeling member do not sufficiently contact each other. Accordingly, it has been difficult to completely remove images.
Furthermore, in color images, in order to enhance the color saturation, the surface of the image forming substance is generally heat fixed until it is smoothed in a seamless manner on the surface of the recording material. For this reason, even if an image removal accelerating liquid is applied from the surface of the image, the image removal accelerating liquid will be blocked by the hydrophobic image forming substance, and therefore the image removal accelerating liquid will not reach into the depth of the paper sheet. Accordingly, it has been difficult to make the image removal accelerating liquid reach the cellulose fiber contacting the image forming substance. Thus, with the image removing method disclosed in this patent document, it has been almost impossible to remove color images.
Furthermore, in a method of applying an image removal accelerating liquid including water to the recording material, even if the amount of water applied as the image removal accelerating liquid is extremely small, the following problem may arise. That is, the paper sheet includes cellulose fiber, and therefore when a repeatedly-used recording material is processed in an image forming apparatus or an image removing device, wrinkles and curls may be formed in the recording material, or paper jamming may occur due to such curls. Therefore, the recording material cannot be repeatedly used many times. Furthermore, if a large amount of water is applied to the recording material, a large amount of power will be required for drying the absorbed water, and the size of the regenerated recording material will change.
Patent document 5 (Japanese Laid-Open Patent Application No. H11-219073) discloses a unit for removing, from a peeling member, an image forming substance that has been transferred from a recording material to the peeling member. Specifically, this patent document discloses a fixed film thickness regulating member that is spaced apart from the peeling member, as well as a film thickness regulating member that is conveyed in a direction counter to the direction in which the peeling member is conveyed. The surface of the movable film thickness regulating member disclosed in this patent document is made of a low-surface-energy material such as Teflon (registered trademark), which has no adhesive force with respect to the image forming substance. Specifically, the basic principle of the unit disclosed in this patent document is that a shearing force is applied to a thermoplastic resin layer on a peeling member and/or a thermoplastic image forming substance that has been transferred from the recording material, in order to scrape off a part of the layer/substance. However, an image forming substance used in a typical electrophotographic device is designed to have a certain level of elasticity and a high level of internal cohesion force even under the fixing temperature, so that it does not adhere to the heat fixing roller or the heat fixing belt. Thus, even if the image forming substance is heated to a temperature higher than the fixing temperature in the image forming apparatus, the cohesion force of the image forming substance will be maintained at a relatively high level. Therefore, even by pressing the image forming substance with a member that has no adhesive force with respect to the image forming substance as disclosed in this reference, it has been difficult to apply, to the image forming substance, a shearing force that exceeds the cohesive force in order to scrape off the image forming substance from the peeling member.
Patent document 6 (Japanese Laid-Open Patent Application No. H7-311520) discloses an image removing device for temporarily transferring, onto a cleaning member, an image forming substance that has been transferred from a recording material to a peeling member. The technology disclosed in patent document 6 is for transferring the image forming function on the peeling member to the cleaning member having a surface made of a material with higher adhesiveness compared to the peeling member, to entirely remove the image forming substance on the peeling member. This cleaning method is for removing the image forming substance that has been transferred from a recording material onto a peeling member without scraping off the image forming substance with a blade, to thereby mitigate attrition of the peeling member and extend the operating life of the peeling member.
In the cleaning unit disclosed in patent document 6, either one of the peeling member or the transfer cleaning member is not directly driven, but is caused to follow the rotation of the other one, so that the peeling member and the transfer cleaning member are conveyed at the same speed. In such a cleaning unit, the transfer cleaning member will need to be made of a material having a significantly higher adhesive force with respect to the image forming substance, compared to that of the peeling member. Otherwise, the image forming substance will not be transferred from the peeling member to the transfer cleaning member. Accordingly, the surface of the peeling member can only be made of a material having a relatively low adhesive force with respect to the image forming substance. In a device for applying an image removal accelerating liquid to a recording material to weaken the adhesive force between the recording material and the image forming substance, and then transferring the image forming substance from the recording material to the peeling member, the image forming substance can be transferred from the recording material even if the peeling member is made of a material having a relatively low adhesive force with respect to the image forming substance. However, in a method where a recording material having a low adhesive force with respect to the image forming substance is used, and the image forming substance is transferred and removed from the recording material to the peeling member without the use of an image removal accelerating liquid, the following condition is essential. That is, in order to make the recording material have practical fixing properties with respect to the image forming substance, the peeling member is to have high adhesiveness with respect to the image forming substance to remove the image forming substance from the recording material. For this reason, it has been difficult to apply the transfer cleaning method disclosed in this patent document to a device for transferring, peeling, and removing an image forming substance without the use of an image removal accelerating liquid.
Patent document 7 (Japanese Laid-Open Patent Application No. H7-56480) discloses a technique of directly removing an image forming substance that has been transferred from a recording material to a peeling member with the use of a flat plate-like blade. This patent document also discloses a method in which the image forming substance that has been transferred onto the peeling member is temporarily transferred onto a cleaning roller, and the image forming substance on the cleaning roller is then removed with a blade. Patent document 7 does not include any detailed descriptions regarding the transfer cleaning method; however, it describes that the transfer cleaning member has releasability with respect to the image forming substance that is lower than its releasability with respect to the peeling member. This is based on the same concept as that of the transfer cleaning unit according to patent document 6.
The following documents disclose recording materials used in an image removing device for removing an image forming substance on a recording material by a heat-transfer process, without using an image removal accelerating liquid.
Patent document 8 (Japanese Laid-Open Patent Application No. 2005-234162) discloses a reusable electrophotographic sheet manufactured as follows. Specifically, a base sheet is collated with a filler layer, which includes a polymer selected from polyvinyl alcohol, starch, carboxymethylcellulose, etc. Then, a composition is applied on this, which includes an image forming substance repellent including a compound including an alkyl group and an alkenyl group of more than or equal to carbon number 6.
Patent document 9 (Japanese Laid-Open Patent Application No. 2006-78618) discloses a reusable material having an olefin/maleic anhydride polymer provided as an image forming substance repellent at least on the side where an image is to be formed.    Patent document 1: Japanese Laid-Open Patent Application No. H4-64472    Patent document 2: Japanese Laid-Open Patent Application No. 2002-72792    Patent document 3: Japanese Laid-Open Patent Application No. 2001-66957    Patent document 4: Japanese Laid-Open Patent Application No. H7-13383    Patent document 5: Japanese Laid-Open Patent Application No. H11-219073    Patent document 6: Japanese Laid-Open Patent Application No. H7-311520    Patent document 7: Japanese Laid-Open Patent Application No. H7-56480    Patent document 8: Japanese Laid-Open Patent Application No. 2005-234162    Patent document 9: Japanese Laid-Open Patent Application No. 2006-78618